Solution speciation controls mercury isotope fractionation of Hg(II) sorption to goethite

Jiskra, Martin and Wiederhold, Jan G. and Bourdon, Bernard and Kretzschmar, Ruben. (2012) Solution speciation controls mercury isotope fractionation of Hg(II) sorption to goethite. Environmental Science and Technology, 46 (12). pp. 6654-6662.

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Official URL: https://edoc.unibas.ch/68591/

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The application of Hg isotope signatures as tracers for environmental Hg cycling requires the determination of isotope fractionation factors and mechanisms for individual processes. Here, we investigated Hg isotope fractionation of Hg(II) sorption to goethite in batch systems under different experimental conditions. We observed a mass-dependent enrichment of light Hg isotopes on the goethite surface relative to dissolved Hg (ε(202)Hg of -0.30‰ to -0.44‰) which was independent of the pH, chloride and sulfate concentration, type of surface complex, and equilibration time. Based on previous theoretical equilibrium fractionation factors, we propose that Hg isotope fractionation of Hg(II) sorption to goethite is controlled by an equilibrium isotope effect between Hg(II) solution species, expressed on the mineral surface by the adsorption of the cationic solution species. In contrast, the formation of outer-sphere complexes and subsequent conformation changes to different inner-sphere complexes appeared to have insignificant effects on the observed isotope fractionation. Our findings emphasize the importance of solution speciation in metal isotope sorption studies and suggest that the dissolved Hg(II) pool in soils and sediments, which is the most mobile and bioavailable, should be isotopically heavy, as light Hg isotopes are preferentially sequestered during binding to both mineral phases and natural organic matter.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften
UniBasel Contributors:Jiskra, Martin
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:13 Feb 2019 10:45
Deposited On:13 Feb 2019 10:44

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